Power Unit Converter — Watts, Kilowatts, Horsepower, BTU/h and More
Convert power units instantly — watts to kilowatts, horsepower to watts, BTU/h to kW. Practical guide to understanding power ratings.
Power ratings show up everywhere — appliance labels, car specs, generator capacities, HVAC systems — and they're almost never in the unit you need. Your AC is rated in tons, your car in horsepower, your generator in kVA, and your electricity bill charges by kilowatt-hours. Converting between them is essential for making informed purchase decisions.
The CalcHub power converter handles all common power units instantly.
Common Power Conversions
| From | To | Multiply by |
|---|---|---|
| 1 watt (W) | kilowatts (kW) | 0.001 |
| 1 kilowatt (kW) | watts (W) | 1,000 |
| 1 horsepower (HP) | watts (W) | 745.7 |
| 1 kilowatt (kW) | horsepower (HP) | 1.341 |
| 1 BTU/hour | watts (W) | 0.2931 |
| 1 ton (cooling) | watts (W) | 3,516.85 |
| 1 ton (cooling) | BTU/hour | 12,000 |
| 1 kVA | kW (at PF 0.8) | 0.8 |
Practical Applications
Home Appliances
Understanding wattage helps you estimate electricity costs:
| Appliance | Typical Wattage | Monthly Cost (₹8/kWh, 8h/day) |
|---|---|---|
| LED bulb | 10W | ₹19 |
| Ceiling fan | 75W | ₹144 |
| Refrigerator | 150W (avg) | ₹288 |
| 1.5 ton AC | 1,500W | ₹2,880 |
| Washing machine | 500W | ₹120 (1h/day) |
| Microwave | 1,200W | ₹58 (15min/day) |
| Desktop computer | 300W | ₹576 |
A 1,500W AC running 8 hours/day for 30 days: 1,500 × 8 × 30 / 1,000 × ₹8 = ₹2,880/month.
Air Conditioning
AC capacity in India is rated in "tons" — a confusing unit that has nothing to do with weight.
- 1 ton of cooling = 12,000 BTU/h = 3,517 watts
- A 1.5 ton AC = 18,000 BTU/h = 5,275 watts of cooling capacity (power consumption is lower due to efficiency)
| Room Size (sq ft) | AC Tonnage Needed |
|---|---|
| Up to 120 | 0.75 ton |
| 120–180 | 1 ton |
| 180–240 | 1.5 ton |
| 240–350 | 2 ton |
Cars and Motors
Engine power is quoted in HP (horsepower) or PS (metric horsepower — nearly identical):
- A 100 HP car ≈ 74.6 kW
- A 5 HP water pump ≈ 3.7 kW
- Electric cars often list kW directly: a 150 kW motor ≈ 201 HP
Generators and Inverters
Generators are often rated in kVA (kilovolt-amperes), not kW:
- kW = kVA × Power Factor
- Most generators have a power factor of 0.8
- A 5 kVA generator delivers about 4 kW of usable power
If your total load is 3 kW, you need at least a 3.75 kVA generator (3 / 0.8). Always size up by 20% for safety margin.
How to Use the CalcHub Power Converter
- Open the Power Converter at CalcHub
- Enter your value
- Select source unit (e.g., "horsepower")
- Select target unit (e.g., "kilowatts")
- Result appears instantly
What's the difference between kW and kWh?
kW (kilowatt) is a rate — how much power is being used at any moment. kWh (kilowatt-hour) is total energy — power × time. A 1 kW heater running for 3 hours uses 3 kWh. Your electricity bill charges per kWh, not per kW.
Why are generators rated in kVA instead of kW?
kVA includes reactive power (from inductive loads like motors and compressors), while kW only counts real/usable power. The ratio between them is the power factor. Since generators can't predict what you'll plug in, they rate in kVA to account for the worst case.
Is 1 HP really the power of one horse?
Approximately. James Watt defined it as the rate at which a horse could do work — about 550 foot-pounds per second. A real horse can briefly exceed 1 HP, but it's roughly right for sustained effort. More useful as a historical oddity than a practical reference.
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